In the interests of the environment, and to comply with increasingly stringent regulatory demands, it is necessary to increase the amount of biofuels used in automotive fuels.
Biofuels are combustible fuels, typically derived from biological sources, which result in a reduction in “well-to-wheels” (i.e. from source to combustion) greenhouse gas emissions. In gasoline fuels for use in spark ignition engines, the most common biofuels are alcohols, in particular ethanol. These are typically blended with more traditional gasoline fuel components. For use in diesel engines, fatty acid methyl esters (FAMEs) such as rapeseed oil methyl ester, soybean oil methyl ester and palm oil methyl ester are the biofuels most commonly blended with conventional diesel fuel components. However, FAMEs and their oxidation products tend to accumulate in engine oil, which has limited their use to 10% v/v or less in fuels burned in many diesel engines. At higher concentrations they can also cause fouling of fuel injectors. FAMEs are also more expensive to produce than ethanol, and their world production levels much lower.
It would be desirable to provide new biofuel-containing compression ignition fuel formulations which could overcome or at least mitigate the above problems.